Field of the Invention
The present invention concerns the technical field of medical equipment, in particular to a radio frequency power calculation apparatus and method for a magnetic resonance imaging system.
Description of the Prior Art
Magnetic resonance imaging (MRI) is an imaging technology involving biomagnetics and nuclear spin that has advanced rapidly with the development of computer technology, electronic circuit technology and superconductor technology. MRI uses a magnetic field and radio frequency (RF) pulses to induce oscillation of precessing hydrogen nuclei (i.e. H+) in human tissue, to generate RF signals which are processed by a computer to form an image. If an object is placed in a magnetic field and irradiated by suitable electromagnetic waves to produce resonance therein, and electromagnetic waves emitted thereby are then analysed, it is possible to learn the positions and types of the atomic nuclei of which the object is composed. On this basis, a precise three-dimensional image of the interior of the object can be generated. For instance, a moving picture of contiguous slices can be obtained by performing an MRI scan of the human brain.
Based on considerations of patient safety, during an MRI scan it is necessary to measure the power of RF signals in real time, to ensure that the RF signal power satisfies the corresponding safety specification. Once RF signals have been amplified, most of the RF signals are sent to a transmission coil via a directional coupler, with the remaining small number of RF signals being used for power measurement.
In the prior art, an RF signal used for power measurement is received by an RF signal receiving method, and the power value of the RF signal is calculated. However, the RF signal receiving method in the prior art is unitary, and cannot ensure patient safety, and the calculation results are inaccurate.